This page made possible by the sponsorship of:
.

Peach Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Peach Mountain Observatory clear sky chart from 2005-11-05 to 2018-03-11.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
37%
16635
15%
49179
10%
16593
42%
16593
20%
34369

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
18%
975
10%
2716
4%
970
23%
970
13%
2140
January16th to endNight
19%
946
8%
2818
2%
946
24%
946
11%
2242
February1st to 15thNight
17%
761
9%
2435
3%
761
23%
761
10%
1887
February16th to endNight
24%
683
14%
2049
5%
683
32%
683
15%
1499
March1st to 15thNight
27%
764
14%
2218
9%
764
32%
764
18%
1607
March16th to endNight
32%
768
18%
2112
10%
768
39%
768
21%
1481
April1st to 15thNight
29%
572
13%
1808
7%
572
35%
572
18%
1264
April16th to endNight
35%
540
19%
1620
8%
540
45%
540
24%
1086
May1st to 15thNight
36%
540
14%
1620
8%
540
42%
540
21%
1131
May16th to endNight
50%
562
15%
1663
11%
561
55%
561
28%
1064
June1st to 15thNight
56%
540
14%
1440
11%
540
60%
540
32%
920
June16th to endNight
58%
540
17%
1440
12%
540
63%
540
34%
919
July1st to 15thNight
66%
510
16%
1360
13%
510
68%
510
39%
824
July16th to endNight
68%
564
19%
1489
15%
531
71%
531
40%
875
August1st to 15thNight
67%
539
20%
1609
16%
536
70%
536
35%
957
August16th to endNight
65%
573
22%
1758
18%
573
68%
573
33%
1044
September1st to 15thNight
58%
657
25%
1917
20%
657
62%
657
35%
1126
September16th to endNight
60%
717
25%
1980
19%
717
63%
717
34%
1219
October1st to 15thNight
45%
720
19%
2058
15%
720
49%
720
26%
1377
October16th to endNight
27%
768
17%
2418
10%
768
36%
768
18%
1682
November1st to 15thNight
35%
760
19%
2471
15%
760
41%
760
21%
1619
November16th to endNight
25%
780
14%
2535
8%
780
32%
780
15%
1829
December1st to 15thNight
19%
816
8%
2733
3%
816
24%
816
10%
2118
December16th to endNight
15%
1040
8%
2912
1%
1040
21%
1040
8%
2459

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
14%8%47%6%35%45%7%33%
49430
Night
15%8%46%5%34446%35%
49356
Cloud CoverDay
14%8%46%6%35%45%7%33%
49440
Night
15%8%36%5%3445%6%35%
49360
TransparencyDay
49%6%11%19%11%1
49125
Night
48%5%12%20%12%1
49179
SeeingDay
17%7%27%23%16%7%
6413
Night
19%8%28%29%13%1
16639

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%16%6%9%8%45%5%35%16%
1552
16th to endDay
16%16%8%9%8%3444417%
1755
February1st to 15thDay
16%13%7%12%8%35%445%20%
1755
16th to endDay
16%12%6%11%8%35%346%20%
1710
March1st to 15thDay
16%12%5%7%5%35%45%6%27%
1968
16th to endDay
18%9%48%5%34446%30%
2112
April1st to 15thDay
19%10%36%5%3445%6%30%
2148
16th to endDay
17%7%26%5%24347%38%
2340
May1st to 15thDay
19%8%36%5%35%446%31%
2331
16th to endDay
13%6%25%5%35%45%7%39%
2449
June1st to 15thDay
10%5%25%5%35%5%5%8%39%
2520
16th to endDay
9%435%6%46%6%7%10%34%
2520
July1st to 15thDay
7%5%245%35%5%6%9%44%
2520
16th to endDay
8%425%6%36%6%7%9%39%
2577
August1st to 15thDay
8%6%26%6%35%6%5%8%39%
2340
16th to endDay
10%6%35%5%35%5%6%9%38%
2441
September1st to 15thDay
12%426%5%4445%8%41%
2031
16th to endDay
10%6%245%3446%8%41%
1980
October1st to 15thDay
14%6%26%5%24447%38%
1902
16th to endDay
20%9%36%6%34346%32%
1803
November1st to 15thDay
15%8%26%5%24446%37%
1717
16th to endDay
17%12%46%6%3445%5%28%
1755
December1st to 15thDay
15%14%7%10%6%345%46%22%
1540
16th to endDay
20%16%8%11%7%3343415%
1664
January1st to 15thNight
22%12%5%8%6%3435%5%23%
2716
16th to endNight
13%12%8%11%8%45%436%20%
2818
February1st to 15thNight
15%14%5%8%6%35%345%25%
2433
16th to endNight
17%10%5%8%5%2445%6%28%
2049
March1st to 15thNight
16%10%45%6%34446%32%
2206
16th to endNight
15%8%35%5%35%45%8%34%
2112
April1st to 15thNight
18%8%345%35%5%5%6%34%
1808
16th to endNight
15%8%245%3445%7%38%
1620
May1st to 15thNight
19%6%16%5%45%448%33%
1620
16th to endNight
13%5%245%25%439%43%
1661
June1st to 15thNight
9%5%245%35%45%8%46%
1440
16th to endNight
8%426%5%245%6%10%44%
1440
July1st to 15thNight
7%314435%45%7%52%
1440
16th to endNight
5%32442445%11%51%
1591
August1st to 15thNight
5%4245%35%5%5%9%48%
1620
16th to endNight
10%4235%23337%51%
1758
September1st to 15thNight
10%5%1432345%6%51%
1917
16th to endNight
11%42442445%7%48%
1980
October1st to 15thNight
15%6%35%4345%46%41%
2058
16th to endNight
20%8%35%5%23435%35%
2418
November1st to 15thNight
14%8%35%5%25%446%39%
2471
16th to endNight
19%11%46%5%23446%30%
2535
December1st to 15thNight
18%13%5%9%6%24446%23%
2733
16th to endNight
21%16%6%9%6%45%44416%
2912

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%16%5%10%7%5%6%436%16%
1552
16th to endDay
16%17%7%10%8%34445%16%
1755
February1st to 15thDay
15%13%7%11%9%35%345%20%
1755
16th to endDay
16%13%5%11%7%25%347%20%
1710
March1st to 15thDay
17%11%5%7%5%3445%6%27%
1979
16th to endDay
18%9%48%6%24346%30%
2111
April1st to 15thDay
20%10%45%5%44446%30%
2148
16th to endDay
16%7%36%5%23346%38%
2340
May1st to 15thDay
18%8%36%6%35%45%6%32%
2331
16th to endDay
13%6%25%5%35%45%7%39%
2449
June1st to 15thDay
10%5%346%36%5%5%9%39%
2520
16th to endDay
9%5%25%5%47%5%8%10%34%
2520
July1st to 15thDay
7%5%34436%46%9%44%
2520
16th to endDay
7%5%25%6%45%6%7%10%39%
2577
August1st to 15thDay
8%6%25%6%45%5%6%9%39%
2340
16th to endDay
10%6%35%5%35%5%6%9%38%
2441
September1st to 15thDay
11%5%25%6%35%45%8%41%
2031
16th to endDay
10%5%25%435%46%8%41%
1980
October1st to 15thDay
14%6%36%6%25%45%6%38%
1902
16th to endDay
20%9%46%6%34336%32%
1803
November1st to 15thDay
15%7%46%5%3445%6%37%
1717
16th to endDay
17%11%47%6%35%446%28%
1755
December1st to 15thDay
15%14%7%10%7%35%346%21%
1540
16th to endDay
20%16%8%10%7%44345%15%
1664
January1st to 15thNight
22%12%5%8%6%33445%23%
2716
16th to endNight
13%13%7%11%7%45%446%20%
2818
February1st to 15thNight
15%15%5%8%7%35%345%25%
2426
16th to endNight
17%10%5%8%6%2445%6%28%
2049
March1st to 15thNight
17%10%46%6%34446%32%
2218
16th to endNight
15%8%35%5%25%45%7%34%
2112
April1st to 15thNight
18%8%35%5%35%45%6%33%
1808
16th to endNight
15%8%245%3445%7%38%
1620
May1st to 15thNight
19%6%16%5%35%448%34%
1619
16th to endNight
12%5%25%5%25%348%43%
1661
June1st to 15thNight
9%4245%35%45%8%46%
1440
16th to endNight
8%326%4346%6%10%43%
1440
July1st to 15thNight
7%2145%3445%8%52%
1440
16th to endNight
442432446%9%52%
1591
August1st to 15thNight
5%415%5%35%5%6%8%48%
1620
16th to endNight
9%425%423446%51%
1758
September1st to 15thNight
10%5%14423446%51%
1917
16th to endNight
10%42443445%7%48%
1980
October1st to 15thNight
14%6%35%5%2445%5%41%
2058
16th to endNight
20%7%35%5%34435%35%
2418
November1st to 15thNight
14%8%26%43435%6%39%
2471
16th to endNight
19%11%45%5%33446%30%
2535
December1st to 15thNight
18%13%6%8%6%35%346%22%
2733
16th to endNight
21%16%5%9%6%45%44416%
2912

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
68%6%10%10%4
1553
16th to endDay
69%411%9%4
1755
February1st to 15thDay
65%5%8%12%6%
1757
16th to endDay
64%410%14%5%
1710
March1st to 15thDay
56%6%11%15%7%1
1979
16th to endDay
54%5%11%19%7%1
2112
April1st to 15thDay
54%410%19%10%
2148
16th to endDay
46%5%13%16%15%2
2340
May1st to 15thDay
52%6%11%18%10%1
2331
16th to endDay
43%6%12%24%11%1
2453
June1st to 15thDay
39%7%12%23%14%1
2520
16th to endDay
41%8%13%20%15%
2520
July1st to 15thDay
35%7%10%24%19%2
2371
16th to endDay
37%8%14%21%15%2
2416
August1st to 15thDay
39%7%12%24%13%1
2327
16th to endDay
40%7%11%22%15%2
2441
September1st to 15thDay
39%6%12%24%14%1
2031
16th to endDay
37%6%11%29%14%
1980
October1st to 15thDay
45%6%11%22%12%2
1902
16th to endDay
53%5%13%18%8%
1803
November1st to 15thDay
47%5%11%21%12%1
1717
16th to endDay
56%5%13%18%6%
1755
December1st to 15thDay
63%412%14%5%
1540
16th to endDay
72%5%11%7%3
1664
January1st to 15thNight
61%411%13%7%
2716
16th to endNight
64%5%13%11%4
2818
February1st to 15thNight
61%6%9%14%6%1
2435
16th to endNight
56%313%17%7%
2049
March1st to 15thNight
52%5%10%18%10%1
2218
16th to endNight
48%5%12%21%11%1
2112
April1st to 15thNight
49%6%10%18%14%
1808
16th to endNight
44%5%11%18%17%2
1620
May1st to 15thNight
49%5%10%20%11%2
1620
16th to endNight
38%6%12%23%15%3
1663
June1st to 15thNight
35%7%12%26%16%1
1440
16th to endNight
33%8%14%25%17%
1440
July1st to 15thNight
29%7%11%28%20%2
1360
16th to endNight
27%7%15%25%20%3
1489
August1st to 15thNight
30%7%13%30%15%2
1609
16th to endNight
33%6%11%26%19%3
1758
September1st to 15thNight
32%410%29%21%1
1917
16th to endNight
33%6%11%29%18%
1980
October1st to 15thNight
42%6%10%22%17%1
2058
16th to endNight
50%412%21%9%
2418
November1st to 15thNight
44%5%12%22%12%1
2471
16th to endNight
54%5%13%18%7%
2535
December1st to 15thNight
62%5%11%13%6%
2733
16th to endNight
70%5%9%10%4
2912

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
21%10%41%20%5%1
135
16th to endDay
31%9%43%12%3
144
February1st to 15thDay
30%18%37%10%2
135
16th to endDay
28%13%39%15%3
120
March1st to 15thDay
27%11%32%22%6%
195
16th to endDay
24%6%31%25%10%1
288
April1st to 15thDay
22%8%33%23%9%2
270
16th to endDay
20%9%31%18%13%7%
270
May1st to 15thDay
22%7%29%20%14%5%
288
16th to endDay
18%7%25%22%16%8%
349
June1st to 15thDay
11%5%30%30%16%5%
495
16th to endDay
10%7%33%27%16%5%
495
July1st to 15thDay
9%425%27%22%10%
475
16th to endDay
7%421%28%26%11%
437
August1st to 15thDay
10%215%28%21%21%
313
16th to endDay
13%418%20%27%16%
332
September1st to 15thDay
11%318%20%25%20%
315
16th to endDay
13%414%21%29%15%
314
October1st to 15thDay
18%5%24%28%16%6%
315
16th to endDay
26%10%27%29%6%
219
November1st to 15thDay
18%9%30%25%13%2
135
16th to endDay
20%20%39%15%5%
135
December1st to 15thDay
21%26%31%11%9%
95
16th to endDay
25%27%34%11%1
144
January1st to 15thNight
27%11%34%20%5%
975
16th to endNight
19%10%37%26%5%
946
February1st to 15thNight
23%12%37%22%3
764
16th to endNight
22%11%33%27%4
683
March1st to 15thNight
22%12%31%26%7%
764
16th to endNight
18%10%33%27%9%1
768
April1st to 15thNight
20%12%32%27%5%
572
16th to endNight
20%6%32%28%9%1
540
May1st to 15thNight
20%5%30%32%10%1
540
16th to endNight
14%326%34%19%2
563
June1st to 15thNight
11%223%46%16%
540
16th to endNight
8%121%44%21%1
540
July1st to 15thNight
10%116%40%28%3
510
16th to endNight
4216%47%26%2
564
August1st to 15thNight
6%117%43%27%3
539
16th to endNight
11%113%34%34%5%
573
September1st to 15thNight
12%419%30%27%5%
657
16th to endNight
11%417%30%29%6%
717
October1st to 15thNight
17%6%23%31%17%2
720
16th to endNight
24%11%33%23%6%
768
November1st to 15thNight
19%9%30%26%12%1
760
16th to endNight
26%11%32%21%7%
780
December1st to 15thNight
25%12%35%21%4
816
16th to endNight
29%10%35%21%3
1040
Page generated at 2018-03-12 13:28:13. Version ac04

Copyright 2018 A. Danko


Peach Mountain Observatory Clear Sky Chart |Charts Home